KANSAS CITY, Mo. (AP) -Three-run homers have gone from uncommon to commonplace for the Baltimore Orioles .

Kevin Millar hit a three-run drive and finished with three hits to help the Orioles beat Kansas City 6-5 on a rainy Saturday night for their 12th straight victory over the Royals.

Millar, who entered hitting just .186 in his previous 15 games, homered just inside the left-field foul pole on a 2-1 pitch from Brett Tomko (1-4) with two out in the first. Brian Roberts and Melvin Mora , both aboard after singles, scored on Millar's fifth home run.

The Orioles have hit three three-run homers in the first three games of the series after coming to Kansas City without a three-run drive this year.

''We haven't swung the bats like we're capable as far as batting average, but I think this team has got some big hits and some timely hits when we need to,'' Millar said. ''I think we've done a good job of clawing and scratching through the struggles.''

Roberts suffered a left foot contusion and did not return after a rain delay of 1 hour, 52 minutes in the first inning.

''That misty rain hit your face and it got cold,'' Millar said. ''It was tough defensively. It was really windy on the field. It was a battle.''

Garrett Olson (2-0) went 5 1-3 innings for Baltimore, allowing three runs and eight hits. Olson, who has a 2.95 ERA, has allowed 16 hits and six earned runs in 18 1-3 innings in three starts since being called up April 29.

''I thought the best thing he did was keep his focus,'' Orioles manager Dave Trembley said. ''I thought it was easy to lose your focus. It's a two-hour rain delay and you're ready to pitch and all of a sudden it's taken away from you. He had to make some big pitches and he got us to where we needed to be.''

Mora singled in Freddie Bynum in the fifth, and the Orioles pushed across two more in the sixth to make it 6-1. Adam Jones hit an RBI triple and scored on Guillermo Quiroz 's squeeze bunt.

Joey Gathright had two bunt singles and stole two bases for Kansas City, which finished with 13 hits.

Gathright and Jose Guillen collected RBIs in the sixth, cutting the lead to 6-3. David DeJesus led off the seventh with a triple against Jamie Walker and scored on Esteban German 's single.

Walker failed to retire any of the three batters he faced and left with runners on the corners and no out. Jim Johnson replaced him and struck out Billy Butler and Mark Grudzielanek before retiring Guillen on a grounder to prevent further damage.

''In that situation with no outs, you're actually going to give up that run to get a double play,'' Johnson said. ''When I got to two strikes on Butler, I've got to take a shot at getting a strikeout. I did it. The same approach with Grudzielanek, the next batter, I was trying to get him to ground into a double play and ended up getting ahead. The key is just being aggressive.''

Said Trembley: ''He used his fastball and pitched inside in a situation where normally pitch you don't pitch inside. He pounded the strike zone down and he pounded the strike zone in. He's stepped up for us and has down an incredible job. The team has confidence in him and I'm not afraid to put him in there in the middle of an inning.''

George Sherrill allowed a run in the ninth before finishing for his 13th save in 15 opportunities. Butler's RBI double to left-center hit high off the fence.

''I can't hit a ball any harder,'' Butler said. ''I thought it was gone when I hit it. I just hit it to the wrong part of the park.''

Tomko gave up six runs and nine hits in 5 1-3 innings. He struck out a season-high eight and did not walk a hitter for the first time this year.

''Anytime they get three hits in an inning they are going to score,'' Tomko said. ''Eight punchouts and no walks, you are on the right track.''

The Royals have lost five of six to begin their 10-game homestand, their longest of the season. The Royals' 6-12 home record is the worst in the majors.

Notes: The last Orioles' streak of more than 12 straight victories over a single team was 15 against Toronto in 1978-79. ... Royals pitchers struck out 12, tying a season high. ... DeJesus started his fourth career game in right.